Researchers at the Lawrence Berkeley National Laboratory, which is under the jurisdiction of the Department of Energy, and the University of California, Berkeley, recently announced that they have developed a new technology that can produce low-cost high-efficiency solar cells of almost any semiconductor material, including those who are present in larger quantities, such as metal oxides, sulfide and phosphide. These materials till now have been considered unstable for making solar cells because it is difficult to adjust their properties by chemical route.

Current photovoltaic technology relies on rare and expensive semiconductor such as silicon crystals, thin layers of copper cadmium telluride or idnium Galen arsenide, which are either expensive or difficult to convert into a final product.

-”It is time to start using and bad materials. Our technology allows us to bypass the problems that occur during chemical-tune the properties of materials that are non-toxic and has a massive scale in the country, by simply applying the electric field” – says Alex Zetl who along with colleague Feng Wang leads this research. The new technology is called screening-engineered field-effect photovoltaics (SFPV) because it uses the electric field, a phenomenon which is very well known and studied, while the concentration of the carriers of electricity in semiconductors changes in an electric field.

With this SFVP technology, carefully designed input electrode allows the electric field in the gate electrode to significantly penetrate and evenly distributes the concentration of carriers and their type to create a p-n junction. This allows the creation of high-quality p-n junctions in semiconductors that would otherwise be difficult or impossible to connect with classical chemical methods.

Photovoltaic Materials

In SFPV system, the structure of the front electrode is also designed to at least one of its dimensions is constant.

For example, in a configuration with copper oxide, researchers at Berkeley have shaped electrode contact in the form of tiny fingers, while in another case, working with silicon, made ultra-thin contact (only one layer of grafen). With enough thin “fingers” the field in the gate creates an inversion layer with low electrical resistance between the “fingers” and a potential barrier under them. Uniformly thin contact allows the field at the gate to enter there easily tunes the carrier concentration, so get high-quality p-n junctions.